The model, in the open

What it does · every reward triggers a fast process and a slower opposing one. The "felt" line in your chart is the first minus the second. Repetition weakens the fast process and strengthens the slow one — same stimulus, less high, more comedown.

Source · Solomon RL & Corbit JD (1974). An opponent-process theory of motivation: I. Temporal dynamics of affect. Psychological Review 81(2):119–145.

Honest note · the structure is a direct statement of the theory. The gain, the sensitization on repetition, and the decay of the b-process are ours to tune.

What it does · your baseline is not fixed. Accumulated unprotected reward drags the setpoint down, and it clears far more slowly than it accumulates. That asymmetry is deliberate — it is the whole reason a bad week costs more than a good week pays.

Source · Koob GF & Le Moal M (1997), Drug abuse: hedonic homeostatic dysregulation, Science 278:52–58; and (2001), Drug addiction, dysregulation of reward, and allostasis, Neuropsychopharmacology 24(2):97–129.

Honest note · allostasis — a chronic deviation of the reward setpoint — is the established mechanism. The rates at which load accumulates, clears, and pulls the tonic baseline are ours.

What it does · an unpredictable reward costs more than a predictable one of the same size. Variable-ratio schedules — your feed — carry the heaviest multiplier, with variable-interval in between and fixed schedules lightest. Variable-ratio events are penalised a second time in peak hygiene.

Source · Ferster CB & Skinner BF (1957). Schedules of Reinforcement.

Honest note · the ordering — variable ratio above variable interval above fixed — is textbook. The specific multipliers are ours and are not measured quantities.

What it does · rewards you worked for are treated as protective; frictionless ones are treated as costly. Protection rises with effort and saturates — more effort helps, but with diminishing returns. This is why Myo never tells you to want less.

Source · Salamone JD & Correa M and colleagues on effort-based decision making — accumbens dopamine depletion impairs willingness to work for a reward while leaving preference for it intact.

Honest note · the literature establishes that effort and reward are dissociable and that dopamine sits on the effort axis. It does not establish a saturating protection function of the exact shape we use. This one is our modeling choice, and it is the most load-bearing assumption in the product.

What it does · craving risk rises with depleted baseline, accumulated load, and the b-process — never with pleasure. There is no "liking" score in Myo, by design.

Source · Robinson TE & Berridge KC (1993), The neural basis of drug craving: an incentive-sensitization theory of addiction, Brain Research Reviews 18(3):247–291; 30-year review in Annual Review of Psychology (2025) 76:29–58.

Honest note · wanting and liking run on dissociable systems, and sensitization amplifies wanting without increasing liking. The structure follows; the weights are ours.

What it does · the effective peak of a reward scales with its magnitude, how novel it is, and the schedule that delivers it. Unpredicted rewards land harder than expected ones.

Source · Schultz W (2016), Dopamine reward prediction-error signalling: a two-component response, Nature Reviews Neuroscience 17(3):183–195.

Honest note · dopamine responses scale with unpredictedness. Treating novelty as a separate factor in the peak is a simplification of a qualitative finding.

What it does · HRV, resting heart rate and sleep enter as corroborating evidence about recovery. They do not feed the reward model.

Honest note · no wearable measures dopamine. Nothing does. Anyone claiming otherwise is selling the same broken premise in nicer packaging. Sleep is the strongest link we have — sleep deprivation is associated with striatal dopamine-receptor downregulation (Volkow ND et al., 2012, Journal of Neuroscience).